My general belief is that when it comes to national security, what we have to focus on is getting things right in the future as opposed to looking at what we got wrong in the past.

- Barack Obama, TV interview about whether he would pursue accountability for the Bush-era torture programme, January 11, 2009

He would have walked away for three quid and the truth. This will be important to recall years down the line, once millions have been spent, pages of comment consumed, and a troupe of witnesses have stood in the dock to prove a story that Britain and America could - and should - have admitted at the start.

This quest for truth, by Libyan revolutionary Abdul-Hakim Belhaj and his wife Fatima Boudchar, is the subject of a new documentary on Al Jazeera this week. The key events date to March 2004, when George Bush's CIA, Tony Blair's MI6, and Muammar Gaddafi's ESO conspired to abduct Abdul-Hakim and his pregnant wife and send them to torture in Thailand and Libya. Tony Blair's famous embrace in the tent with Gaddafi followed not three weeks later. Just days after that, Belhaj's compatriot Sami al-Saadi was likewise seized and sent to Libya with his wife and four children. Reprieve is advising both families in a multi-continent search for accountability and an honest reckoning.

As the documentary suggests, these were not isolated wrongs but matters of high government policy. Belhaj, al-Saadi, and their families were the human fee the US and UK paid to bring Gaddafi ‘in from the cold’ and get him to give up chemical weapons. Until Libya's 2011 revolution, when Human Rights Watch and others unearthed this dark side of the 'deal in the desert,' some saw the West's rapprochement with Gaddafi as a victory. It was said to be the crowning achievement of Sir Mark Allen, then MI6's counter-terror chief.

What Sir Mark, reportedly a devout Catholic, thought about trading the fates of these two families we still do not know. Traditional Catholic theology shuns the idea that the ends justify the means. How did he square the operation with his own conscience? We know even less about the views of Jack Straw, who apparently authorized the rendition, or Tony Blair, who took a keen interest in making Gaddafi an ally. These are just a few of the untold truths Belhaj and his wife are struggling to uncover.

Nor were these the only families who suffered for the West’s deal with Gaddafi. My clients' torture - and the false 'evidence' it invariably yields - disrupted the lives of countless others. The documentary touches on this, but it is possible we will never know how many hapless souls in Libyan jails and beyond were abused with some piece of nonsense beaten out of Belhaj and al-Saadi. This is another reason the truth of what the US and UK did must be told.

These are truths both the British and American governments are desperate to avoid. You might ask why, given that both nations are now ruled by parties who are not to blame for the renditions. But it seems Nelson Mandela understood something Barack Obama (and David Cameron) do not: political vengeance is caustic, but so is amnesia. He felt apartheid’s legacy would tear South Africa apart without some effort to air what happened. And so there was an exchange: reconciliation, yes, but only after truth.

Belhaj saw the value of this. It is why he offered to settle his UK case, if only Britain would admit what it had done. The British government has, to date, refused. Without a leader of Mandela's vision in Britain or the US, Abdul-Hakim and Fatima are left to press for truth in the face of fierce resistance from both governments.

And let us face it: that resistance tends to succeed. It is a bald fact that the US, with ample assistance from the UK and others, ran a global system of secret prisons and abductions and has largely gotten away with it.

During the 'war on terror' hundreds were tortured and some disappeared. To this day, the US has not apologized to or compensated a single torture victim. It has not sanctioned any torturer. Instead US officials go on American talk shows and boast about waterboarding and swear to do it all again when the opportunity arises. In the handful of countries who have paid torture victims, including here in Britain, there have typically been no admissions, no apologies, and certainly no individual findings of responsibility.

This is the boil we must lance. It is, to steal Mandela's phrase, the 'festering sore' at the heart of democracies who waged the 'war on terror'. It demeans every society who took part. It makes us hypocrites in the eyes of fledgling (and struggling) democracies across the Middle East.

"True reconciliation," Mandela said, "does not consist in merely forgetting the past." If Cameron and Obama will not lead a reckoning, we will have to trust to the fortitude of people like Abdul-Hakim and Fatima to do it for them.

Cori Crider is the legal director at Reprieve, a legal aid organisation.